In 1991, Benny Shanon, a respected professor of psychology at Hebrew University in Jerusalem, flew to Brazil to participate in a scientific conference. After it ended, he travelled to an Amazonian outpost called Colonia. Shanon's curiosity had been piqued by reports that members of a church in Colonia consumed a psychotropic tea called
ayahuasca, brewed from two rain-forest plants. Long prized by rain-forest Indians for its visionary properties,
ayahuasca has recently become a sacrament for several churches in Brazil and for a growing number of spiritual seekers in the U.S. and Europe.

Shanon ended up ingesting
ayahuasca in Colonia, and the experience moved him so deeply that he spent next decade exploring the tea's significance. He drank
ayahuasca himself more than 100 times in many different settings, interviewed scores of people who had done so and read all he could find on
ayahuasca and other mind-altering substances. He then poured his findings and reflections into a 400-plus-page book,
The Antipodes of the Mind, published in 2003.

Shanon's title alludes to a line in Aldous Huxley's essay
The Doors of Perception. The reference is fitting, because Shanon's brilliant book is itself an instant classic of the literature on altered states. It deserves to be placed in the same category as Huxley's work and
The Varieties of Religious Experience, by William James.

Unlike some psychedelic authors, Shanon is earnest, serious, straightforward and absolutely trustworthy. He is a true scientist, dedicated to precise reporting and careful analysis rather than to entertainment. Not that his book is dull. Far from it.
Antipodes is suffused with a sense of adventure, of a kind that has virtually vanished from modern science. Plunging into the depths of his own
ayahuasca -intoxicated mind, Shanon resembles one of the great Victorian explorers trekking into uncharted wilds, maintaining his equilibrium and wits even in the face of the most fantastical sights.

Inner space, Shanon reminds us, truly is the last great frontier of science

Like Darwin on the voyage of the Beagle, Shanon is concerned primarily with collecting and categorizing data rather than theorizing. But he also ponders his and others' experiences and draws some tentative conclusions. While believing that
ayahuasca can be genuinely revelatory, he cautions that it can also be "the worst of liars." He remains skeptical of occult claims often made for the tea - that it puts us in touch with ghosts, makes us clairvoyant, lets us leave our bodies and travel astrally.
Ayahuasca visions are products of the imagination, Shanon suggests, rather than glimpses of a supernatural realm existing in parallel to our own.

This proposal will sound reductionist to some, but it is actually quite provocative and raises many questions requiring further consideration. Why does the imagination, when stimulated by
ayahuasca, yield visions so much more vivid and powerful than those we encounter in ordinary dreams? Why do
ayahuasca -drinkers from widely disparate cultures so often hallucinate similar phenomena, such as jaguars and snakes, or palaces and royalty? Why are the visions of even an areligious person like Shanon so often laden with religious significance?

Shanon is particularly fascinated by the fact that
ayahuasca so often induces sensation of self-transcendence and unity: "With this brew, the boundaries between me and the world, between me and other human beings, between the human and even the Divine are blurred and even transgressed." These are the hallmarks of mystical experiences, whether induced by drugs, meditation or other means.

Ayahuasca, Shanon concludes, is rightly called a sacrament, because it "introduces one to realms that pertain to religion, to faith, to the Divine."
Ayahuasca left Shanon himself profoundly transformed. "For years I have characterized myself as a 'devout atheist,'" he writes. "When I left South America I was no longer one." Although he does not advocate any particular religious faith, his experiences led him to suspect that the "'perennial philosophy' both advocated by mystics throughout the ages and cultures and suggested by various individuals who have partaken of
ayahuasca is actually the true metaphysics."

Antipodes will no doubt be eagerly seized upon by the psychedelic intelligentsia. But it deserves to be read by anyone interested in religion, mysticism and consciousness - and who is not? It should be required reading for psychologists, psychiatrists and neuroscientists, because it shows how absurdly simplistic are the biochemical, Darwinian and genetic models now dominating mind science. Inner space, Shanon reminds us, truly is the last great frontier of science, and its reaches are vast and wild and mysterious.

John Horgan is a science journalist and director of the Center for Science Writings at Stevens Institute of Technology, Hoboken, N.J. His most recent book is Rational Mysticism.